Pain and analgesia in labour

Question 1

What type of pain predominates the first stage of labour?

Answer 1

Visceral pain caused by uterine contractions and cervical dilatation.

Transmitted through T10 to L1 spinal nerves.

Poor localisation.

Question 2

What type of pain predominates the second stage of labour?

Answer 2

Visceral AND somatic pain.

Somatic pain is caused by ligament stretching, ischaemia and injury of the pelvic floor, vagina and perineum.

Transmitted by:

• Pudendal nerve and perineal br of the posterior cutaneous nerve of the thigh –> S2-4
• Cutaneous br of ilioinguinal and genitofemoral nerves to L1-2

Sharp and well localised.

Question 3

Describe the pain pathway for visceral pain

Answer 3

Small unmyelinated ‘C’ fibres –> travel with sympathetic fibres –> uterine, cervical and hypogastric nerve plexuses –> main sympathetic chain –> white rami and into posterior nerve roots of T10 and L1 –> dorsal horn of spinal cord

Question 4

Describe the pain pathway for somatic pain

Answer 4

Fine myelinated rapidly transmitting ‘A delta’ fibres –> S2-4 and L1-2 –> dorsal horn cells –> spino-thalamic tract –> brain

Question 5

According to the Cochrane review 2018 on labour pain management:

What methods of pain relief are shown to be EFFECTIVE?

Answer 5

Pharmacological:
- Epidural

Non-pharmacological:
- Continuous 1:1 support and care provider

Question 6

According to the Cochrane review 2018 on labour pain management:

What methods of pain relief MAY BE EFFECTIVE?

Answer 6

Pharmacological:

• Remifenatil PCA
• Entonox

Non-pharmacological: nil.

Question 7

According to the Cochrane review 2018 on labour pain management:

What methods of pain relief have INSUFFICIENT EVIDENCE to show effectiveness?

Answer 7

Pharmacological:
- Opioids

Non-pharmacological:

• Hypnobirthing and hypnosis
• Aromatherapy
• TENS

Question 8

What are contraindications for a neuraxial block?

Answer 8

• Coagulopathy: Plt <80, INR >1.4
• Maternal refusal
• Local and untreated systemic infection
• Uncontrolled hypovolaemia or haemorrhage
• Expectation of significant haemorrhage
• Certain spinal surgery and abnormalities
• Lack of trained staff to provide safe care.

Question 9

List the side effects of a neuraxial block

Answer 9

Adverse obstetric outcomes:

• Fetal distress
• Uterine hyperstimulation
• Maternal hypotension
• Prolonged second stage.
• Failure 1:10
• Hypotension 1:50
• Pruritis
• Nausea and vomiting
• Urinary retention
• Shivering
• High block: inadvertent epidural dose given into subarachnoid or sudural space OR overdose of spinal anaesthesia
• Local anaesthetic systemic toxicity
• Dural puncture headache 1:100
• Nerve damage very rare
• Respiratory depression rare
• Epidural abscess or meningitis <1:50,000
• Dural haematoma 0.6:100,000

Question 10

List indications for early epidural in labour

Answer 10

• Twin pregnancy
• Preeclampsia
• Obesity BMI >40 or with OSA.
• Difficult airway
• VBAC
• Previous PPH
• History of malignant hyperthermia
• Maternal cardiac and respiratory disease
• Intracranial disease
• Breech
• Intrauterine death

Question 11

List the signs and symptoms of local anaesthetic systemic toxicity

Answer 11

CNS:

• Tinnitus
• Metallic taste
• Agitation
• Dysarthria
• Circumoral tingling
• Paraesthesia
• Seizures
• Loss of consciousness
• Respiratory arrest

Cardiovascular:

• Hypotension
• Arrhythmias
• Cardiac arrest

Question 12

Outline management specific for LAST

Answer 12

• Intralipid (20% lipid emulsion)
• Benzodiazepines for seizures
• Amiodarone for arrhythmias and manage cardiac arrest as per ACLS.
• Cardiopulmomary bypass if doesn’t respond to lipid emulsion and ACLS.